Neutral particle beam processing apparatus

ABSTRACT

A neutral particle beam processing apparatus comprises a workpiece holder ( 20 ) for holding a workpiece (X), a plasma generator for generating a plasma in a vacuum chamber ( 3 ), an orifice electrode ( 5 ) disposed between the workpiece holder ( 20 ) and the plasma generator, and a grid electrode ( 4 ) disposed upstream of the orifice electrode ( 5 ) in the vacuum chamber ( 3 ). The orifice electrode ( 5 ) has orifices ( 5   a ) defined therein. The neutral particle beam processing apparatus further comprises a voltage applying unit for applying a voltage between the orifice electrode ( 5 ) and the grid electrode ( 4 ) via a dielectric ( 5   b ) to extract positive ions from the plasma generated by the plasma generator and pass the extracted positive ions through the orifices ( 5   a ) in the orifice electrode ( 5 ).

TECHNICAL FIELD

[0001] The present invention relates to a neutral particle beamprocessing apparatus, and more particularly to a neutral particle beamprocessing apparatus for generating a highly directional and highlydense neutral particle beam from a high-density plasma and processing aworkpiece with the generated neutral particle beam.

BACKGROUND ART

[0002] In recent years, semiconductor integrated circuits, informationstorage media such as hard disks, micromachines, and the like have beenprocessed in highly fine patterns. In the fields of processing suchworkpieces, attention has been attracted to the use of an energetic beamsuch as a high-density ion beam which is highly linear, i.e., highlydirectional, and has a relatively large beam diameter. For example, theenergetic beam is applied to a workpiece for depositing a film thereonor etching the workpiece.

[0003] As beam sources of such energetic beams, there have been usedbeam generators which generate various kinds of beams including apositive ion beam, a negative ion beam, and a radical beam. The positiveion beam, the negative ion beam, or the radical beam is applied to adesired area of a workpiece from the beam source, for thereby locallydepositing a film on the workpiece, etching the workpiece, modifying thesurface of the workpiece, or joining or bonding parts of the workpiece.

[0004] In the case of a beam source which applies charged particles suchas positive ions or negative ions to a workpiece, an insulated workpiececannot be processed because of a charge build-up phenomenon in whichelectric charges are built up on the workpiece. Further, since the ionbeam emitted from the beam sourc t nds to spread due to the space-chargeeffect, the workpiece cannot be processed in a fine pattern.

[0005] In order to solve the above problems, there has been proposed amethod of introducing electrons into the ion beam to neutralize theelectric charges. This method can balance the electric charges on theworkpiece on the whole. However, since local unbalance of the electriccharges still remains on the workpiece, the workpiece cannot beprocessed in a fine pattern.

[0006] In the case where ions are extracted from a plasma source andapplied to a workpiece, if a radiation (e.g., an ultraviolet ray)produced by the plasma source is applied to the workpiece, then theradiation adversely affects the workpiece. Thus, it is necessary toshield the workpiece from an adverse radiation (e.g., an ultravioletray) emitted from the plasma source.

DISCLOSURE OF INVENTION

[0007] The present invention has been made in view of the abovedrawbacks. It is therefore an object of the present invention to providea neutral particle beam processing apparatus which can apply anenergetic beam having a large beam diameter to a workpiece with aninexpensive and compact structure, and can neutralize ions with a highneutralization efficiency to process the workpiece without a chargebuild-up or damage.

[0008] According to a first aspect of the present invention, there isprovided a neutral particle beam processing apparatus comprising: aworkpiece holder for holding a workpiece; a plasma generator forgenerating a plasma in a vacuum chamber; an orifice electrode disposedbetween the workpiece holder and the plasma generator, the orificeelectrode having orifices defined therein; a grid electrode disposedupstream of the orifice electrode in the vacuum chamber; and a voltageapplying unit for applying a voltage between the orifice electrode andthe grid electrode via a dielectric to extract positive ions from theplasma generated by the plasma generator and pass the extracted positiveions through the orifices in the orifice electrode.

[0009] With the above arrangement, since the workpiece can be processedby a neutral particle beam having no electric charges but having a largetranslational energy, various processes including an etching process anda deposition process can be performed on the workpiece with highaccuracy in such a state that an amount of charge build-up is reduced.Particularly, when the orifice electrode is used for neutralizing thenegative ions, a high neutralization efficiency can be obtained, andhence a beam diameter of an energetic beam can be increasedinexpensively without increasing the size of the apparatus. Further,since the generated plasma is isolated from the workpiece by the orificeelectrode, a radiation produced by the plasma is not substantiallyapplied to the workpiece. Therefore, it is possible to reduce adverseeffects on the workpiece due to the radiation such as an ultraviolet raywhich would otherwise damage the workpiece.

[0010] According to a second aspect of the present invention, there isprovided a neutral particle beam processing apparatus comprising: aworkpiece holder for holding a workpiece; a plasma generator forgenerating a plasma in a vacuum chamber; an orifice electrode disposedbetween the workpiece holder and the plasma generator, the orificeelectrode having orifices defined therein; a grid electrode disposedupstream of the orifice electrode in the vacuum chamber; and a voltageapplying unit for applying a high-frequency voltage between the orificeelectrode and the grid electrode via a dielectric to generate a plasmabetween the orifice electrode and the grid electrode and to extractpositive ions from the generated plasma and pass the extracted positiveions through the orifices in the orifice electrode.

[0011] With the above arrangement, the orifice electrode serves not onlyto neutralize the positive ions, but also to generate the plasma.Therefore, a high neutralization efficiency can be obtained by theorifice electrode, and simultaneously it is not necessary to provide aseparate plasma generator for generating a plasma. Thus, the neutralparticle beam processing apparatus can be made compact in structure, anda beam diameter of an energetic beam can be increased inexpensively.

[0012] According to a preferred aspect of the present invention, thedielectric comprises a dielectric film covering a surface of the orificeelectrode. When the surface of the orifice electrode is covered with adielectric film, more electrons are charged on the dielectric film withweak bonding energies than usual. Therefore, the positive ions that arepassing through the orifices have a higher probability of recombinationwith the electrons. Accordingly, the neutralization efficiency ofpositive ions can further be enhanced.

[0013] The above and other objects, features, and advantages of thepresent invention will be apparent from the following description whentaken in conjunction with the accompanying drawings which illustratespreferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF DRAWINGS

[0014]FIG. 1 is a schematic view showing a whole arrangement of aneutral particle beam processing apparatus according to a firstembodiment of the present invention;

[0015]FIG. 2A is a perspective view showing an orifice electrode in theneutral particle beam processing apparatus shown in FIG. 1;

[0016]FIG. 2B is a vertical cross-sectional view partially showing theorifice electrode shown in FIG. 2A;

[0017]FIG. 3 is a graph showing the potential of a plasma and thepotential of the orifice electrode in the first embodiment of thepresent invention;

[0018]FIG. 4 is a schematic view showing a whole arrangement of aneutral particle beam processing apparatus according to a secondembodiment of the present invention;

[0019]FIG. 5 is a timing chart showing operating states of the neutralparticle beam processing apparatus shown in FIG. 4; and

[0020]FIG. 6 is a timing chart showing an example of a voltage to beapplied instead of a low-frequency voltage.

BEST MODE FOR CARRYING OUT THE INVENTION

[0021] A neutral particle beam processing apparatus according to a firstembodiment of the present invention will be described in detail belowwith reference to FIGS. 1 through 3.

[0022]FIG. 1 is a schematic view showing a whole arrangement of aneutral particle beam processing apparatus according to a firstembodiment of the present invention, with electric components in blockform. As shown in FIG. 1, the neutral particle beam processing apparatuscomprises a cylindrical vacuum chamber 3 constituted by a beamgenerating chamber 1 for generating a neutral particle beam and aprocess chamber 2 for processing a workpiece X such as a semiconductorsubstrate, a glass workpiece, an organic workpiece, a ceramic workpiece,or the like. The vacuum chamber 3 is a metallic chamber, which is madeof metal, and a thin-plate grid electrode 4 made of an electricallyconductive material is disposed in an upstream end of the vacuum chamber3. The vacuum chamber 3 and the grid electrode 4 are electricallyconnected to each other and electrically grounded. The grid electrode 4may comprise a meshed wire, a punching metal, or the like.

[0023] The beam generating chamber 1 has a gas inlet port 11 defined inan upper portion thereof for introducing a gas into the beam generatingchamber 1. The gas inlet port 11 is connected through a gas supply pipe12 to a gas supply source 13, which supplies a gas such as SF₆, CHF₃,CF₄, Cl₂, Ar, O₂, N₂, and C₄F₈ to the beam generating chamber 1.

[0024] The process chamber 2 houses a workpiece holder 20 therein forholding a workpiece X. The workpiece X is placed on an upper surface ofthe workpiece holder 20. The process chamber 2 has a gas outlet port 21defined in a sidewall thereof for discharging the gas from the processchamber 2. The gas outlet port 21 is connected through a gas outlet pipe22 to a vacuum pump 23, which operates to maintain the process chamber 2at a predetermined pressure.

[0025] An orifice plate (orifice electrode) 5 made of an electricallyconductive material such as aluminum is disposed in the lower end of thebeam generating chamber 1. The orifice electrode 5 is electricallyconnected to an AC power supply (voltage applying unit) 100. The vacuumchamber 3 and the orifice electrode 5 are electrically insulated fromeach other by an insulating material (not shown).

[0026]FIG. 2A is a perspective view showing the orifice electrode 5, andFIG. 2B is a vertical cross-sectional view partially showing the orificeelectrode 5 shown in FIG. 2A. As shown in FIGS. 2A and 2B, the orificeelectrode 5 has a number of orifices 5 a defined therein. As shown inFIG. 2B, the surfaces of the orifice electrode 5 are covered withdielectric films 5 b. The dielectric films 5 b may comprise aluminumoxide films. Alternatively, the dielectric films 5 b may comprisenitride films or oxide films which are formed on a silicon material ordielectric films spray-coated on an electrically conductive material.

[0027] Operation of the neutral particle beam processing apparatusaccording to the first embodiment will be described below. FIG. 3 is agraph showing the potential of the plasma and the potential of theorifice electrode 5 in the present embodiment. In FIG. 3, T representsthe period of the potentials.

[0028] The vacuum pump 23 is driven to evacuate the vacuum chamber 3,and then a gas such as SF₆, CHF₃, CF₄, Cl₂, Ar, O₂, N₂, or C₄F₈ isintroduced from the gas supply source 13 into the beam generatingchamber 1. A high-frequency voltage having a frequency of about 13.56MHz is applied to the orifice electrode 5, so that a high-frequencyelectric field is produced in the beam generating chamber 1. The gasintroduced into the beam generating chamber 1 is ionized by electronsthat are accelerated by the high-frequency electric field, for therebygenerating a high-density plasma in the beam generating chamber 1. Theplasma is mainly composed of positive ions and heated electrons.

[0029] At this time, since the electrons, which move 1000 times fasterthan the ions, reach a cathode earlier than the ions to negativelycharge the cathode. This potential attracts the positive ions to thecathode. Since the orifice electrode 5 is electrically insulated by thedielectric films 5 b, the surfaces of the dielectric films 5 b of theorifice electrode 5 are charged with the electrons. Therefore, afterseveral cycles of the high-frequency electric field, a steady state isestablished to prevent el ctrons from excessively passing through theorifice electrode 5. Thus, a sheath is formed upstream of the orificeelectrode 5. The positive ions are accelerated by an average potential(self-bias) of the sheath.

[0030] Then, the positive ions 6 (see FIG. 2B) accelerated by the sheathare introduced into the orifices 5 a defined in the orifice electrode 5.Most of the positive ions 6 that are passing through the orifices 5 a inthe orifice electrode 5 are collided with the sidewall surfaces of theorifices 5 a and hence neutralized in the vicinity of solid sidewallsurfaces of the orifices 5 a, or are collided with gas moleculesremaining within the orifices 5 a and hence neutralized by chargeexchange with the gas molecules, or are collided with electrons chargedon the dielectric films 5 b of the orifice electrode 5 and henceneutralized by recombination with the electrons. Thus, the positive ions6 are converted into neutral particles 7 (see FIG. 2B). Since thedielectric films 5 b are formed on the orifice electrode 5, moreelectrons are charged on the dielectric films 5 b than usual. Therefore,the positive ions 6 that are passing through the orifices 5 a have ahigher probability of recombination with the electrons. Accordingly, aneutralization efficiency of positive ions can be enhanced.

[0031] The positive ions 6 that have been neutralized when passingthrough the orifices 5 a, i.e., the neutral particles 7, are thenemitted as an energetic beam into the process chamber 2. The neutralparticles 7 travel directly in the process chamber 2 and are applied tothe workpiece X placed on the workpiece holder 20, for thereby etchingthe surface of the workpiece X, cleaning the surface of the workpiece X,modifying (e.g., nitriding or oxidizing) the surface of the workpiece X,or depositing a film on the workpiece X.

[0032] The orifice electrode 5 serves not only to neutralize thepositive ions, but also to prevent a radiation produced by the plasmafrom being applied to the workpiece X. Specifically, since the beamgenerating chamber 1 where the plasma is generated is isolated from theworkpiece X by the orifice electrode 5, the radiation produced by theplasma is not substantially applied to the workpiece X. Therefore, it ispossible to reduce adverse effects on the workpiece X due to theradiation such as an ultraviolet ray which would otherwise damage theworkpiece X.

[0033] As well known in the art, when an insulated workpiece such as aworkpiece made of glass or ceramics is processed, charge build-up may bedeveloped on the surface of the insulated workpiece. However, byapplying neutralized particles to the insulating workpiece as describedabove, various processes including an etching process and a depositionprocess can be performed on the insulating workpiece with high accuracyin such a state that an amount of charge build-up is reduced. Varioustypes of gases may be introduced into the beam generating chamber 1according to the type of process to be performed on the workpiece X. Forexample, in a dry etching process, oxygen or a halogen gas mayselectively be used according to the kind of the workpiece X.

[0034] A neutral particle beam processing apparatus according to asecond embodiment of the present invention will be described below withreference to FIGS. 4 and 5. FIG. 4 is a schematic view showing a wholearrangement of a neutral particle beam processing apparatus according toa second embodiment of the present invention, with electric componentsin block form. In FIG. 4, like parts and components are denoted by thesame reference numerals and characters as those of the first embodimentand will not be described below.

[0035] While the vacuum chamber is a metallic chamber in the firstembodiment, a vacuum chamber in the second embodiment comprises a beamgenerating chamber 1 having walls made of quartz glass or ceramics, anda process chamber 2 having walls made of metal. The b am generatingchamber 1 has a coil 10 disposed therearound for inductively coupledplasma (ICP). The coil 10 is housed in a water-cooled tube having anoutside diameter of 8 mm, for example. The coil 10 of about two turns iswound around the beam generating chamber 1. The coil 10 is electricallyconnected to a high-frequency power supply 102, which applies ahigh-frequency voltage having a frequency of about 13.56 MHz, forexample, to the coil 10. When a high-frequency current is supplied fromthe high-frequency power supply 102 to the coil 10, an induced magneticfield is produced in the beam generating chamber 1 by the coil 10. Thevarying magnetic field induces an electric field. The electric fieldaccelerates electrons, which ionizes atoms and molecules in a gas togenerate a plasma in the beam generating chamber 1. Thus, the coil 10and the high-frequency power supply 102 constitute a plasma generatorfor generating a plasma in the beam generating chamber 1.

[0036] The orifice electrode 5 is electrically connected to alow-frequency power supply (voltage applying unit) 103, which applies alow-frequency voltage having a frequency of about 400 kHz, for example,to the orifice electrode 5. A thin-plate grid electrode 40 made of anelectrically conductive material is disposed upstream of the coil 10 andelectrically grounded.

[0037] Operation of the neutral particle beam processing apparatusaccording to the second embodiment will be described below. FIG. 5 is atiming chart showing operating states of the neutral particle beamprocessing apparatus shown in FIG. 4. In FIG. 5, Va represents thepotential of the coil 10, and Vb represents the potential of the orificeelectrode 5. The timing chart is schematically shown in FIG. 5, and theshown frequencies are different from the actual frequencies, forexample.

[0038] The vacuum pump 23 is driven to evacuate the vacuum chamber 3,and then a gas is introduced from the gas supply source 13 into the beamgenerating chamber 1. As shown in FIG. 5, a high-frequency voltagehaving a frequency of about 13.56 MHz is applied to the coil 10 by thehigh-frequency power supply 102, so that a high-frequency electric fieldis produced in the beam generating chamber 1. The gas introduced intothe beam generating chamber 1 is ionized by electrons that areaccelerated by the high-frequency electric field, for thereby generatinga high-density plasma in the beam generating chamber 1.

[0039] At the same time when the high-frequency voltage is applied bythe high-frequency power supply 102, a low-frequency voltage having afrequency of about 400 kHz is applied between the grid electrode 40 andthe orifice electrode 5 by the low-frequency power supply 103. When apositive voltage is applied to the orifice electrode 5 (for example,during a period “A” illustrated in FIG. 5), electrons in the generatedplasma is attracted to the orifice electrode 5 to charge the surfaces ofthe orifice electrode 5 with the electrons. When a negative voltage isapplied to the orifice electrode 5 (for example, during a period “B”illustrated in FIG. 5), positive ions in the generated plasma isattracted to the orifice electrode 5 and pass through the orifice 5 adefined in the orifice electrode 5. Most of the positive ions that arepassing through the orifices 5 a are neutralized and converted intoneutral particles as in the case of the first embodiment. The neutralparticles are then emitted as an energetic beam into the process chamber2. The neutral particles travel directly in the process chamber 2 andare applied to the workpiece X placed on the workpiece holder 20.

[0040] In the present embodiment, the plasma is generated with use of acoil for ICP. However, the plasma may be generated with use of anelectron cyclotron resonance source (ECR source), a coil for heliconwave plasma, a microwave, or the like. The frequency of thehigh-frequency voltage is not limited to 13.56 MHz, but may be in therange from 1 MHz to 20 GHz. Further, the frequency of the high-frequencyvoltage is not limited to 400 kHz. For example, a voltage of arectangular wave as shown in FIG. 6 may be applied instead of thelow-frequency voltage.

[0041] In the above embodiments, the dielectric films are formed on theorifice electrode. As a dielectric, a blocking capacitor may be insertedbetween the AC power supply 100 and the orifice electrode 5 in FIG. 1 orbetween the low-frequency power supply 103 and the orifice electrode 5in FIG. 4.

[0042] Although certain preferred embodiments of the present inventionhave been shown and described in detail, it should be understood thatvarious changes and modifications may be made therein without departingfrom the scope of the appended claims.

Industrial Applicability

[0043] The present invention is suitable for use in a neutral particlebeam processing apparatus for generating a highly directional and highlydense neutral particle beam from a high-density plasma and processing aworkpiece with the generated neutral particle beam.

1. A neutral particle beam processing apparatus comprising: a workpieceholder for holding a workpiece; a plasma generator for generating aplasma in a vacuum chamber; an orifice electrode disposed between saidworkpiece holder and said plasma generator, said orifice electrodehaving orifices defined therein; a grid electrode disposed upstream ofsaid orifice electrode in said vacuum chamber; and a voltage applyingunit for applying a voltage between said orifice electrode and said gridelectrode via a dielectric to extract positive ions from the plasmagenerated by said plasma generator and pass the extracted positive ionsthrough said orifices in said orifice electrode.
 2. A neutral particlebeam processing apparatus according to claim 1, wherein said dielectriccomprises a dielectric film covering a surface of said orificeelectrode.
 3. A neutral particle beam processing apparatus comprising: aworkpiece holder for holding a workpiece; a plasma generator forgenerating a plasma in a vacuum chamber; an orifice electrode disposedbetween said workpiece holder and said plasma generator, said orificeelectrode having orifices defined therein; a grid electrode disposedupstream of said orifice electrode in said vacuum chamber; and a voltageapplying unit for applying a high-frequency voltage between said orificeelectrode and said grid electrode via a dielectric to generate a plasmabetween said orifice electrode and said grid electrode and to extractpositive ions from the generated plasma and pass the extracted positiveions through said orifices in said orifice electrode.
 4. A neutralparticle beam processing apparatus according to claim 3, wherein saiddielectric comprises a dielectric film covering a surface of saidorifice electrode.